PH25 Wildlife Ecotoxicology II
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(PH291) Mercury concentrations in wading birds in relation to trophic position.

Bryan, A.1, Brant, H.1, Romanek, C.1, Jagoe, C.1, Brisbin, I.1, 1 Savannah River Ecology Laboratory, Aiken, SC, USA

ABSTRACT- Variation of mercury concentrations has been previously linked to trophic levels (greater Hg with higher trophic position)in many organisms. We tested this prediction with nestlings of 4-5 wading bird species of varying trophic position in both coastal and inland colonies. We confirmed trophic positions of individual species by stable nitrogen analyses. Generally, the expected relationship between mercury and trophic position was observed for inalnd wading birds. However, the same was not true for all coastal wading birds. Since prey type (fresh- vs. saltwater) can influence mercury bioavailability to coastal birds, we also analyzed for carbon isotopes. Species utilizing saltwater prey were lowest in mercury but among the highest in trophic position. Species utilizing freshwater or a combination of fresh- and saltwater prey tended to have mercury concentrations more related to trophic position. For coastal wading birds, use of different foraging habitat types confounds the relationship of trophic position and mercury accumulation.

Key words: stable isotopes, mercury, trophic position, wading birds

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